Components of the kallikrein-kinin system are present and active within the kidney. They may participate in the regulation of renal excretory and hemodynamic functions. The objective of this project is to define a role for the kallikrein-kinin system in the regulation of renal tubular electrolyte and water transport. A variety of renal micropuncture techniques, including tubular fluid collections at different sites along the nephron, tracer microinjections and servonulling pressure recordings from microvasculatory and tubular elements, will be utilized in rats to evaluate the effects of enhanced and suppressed kinin activity. Kallidin, bradykinin, blockers and stimulants of the intrarenal kinin generating system will be administered by intratubular, close arterial, and peritubular vascular routes. The nephron segment primarily affected by kinins and whether they exert an inhibitory action on transport processes predominantly from the luminal or peritubular side will be examined. The possible mediation of the renal actions of kinins by prostaglandins will be evaluated by performing these experiments in the presence and absence of prostaglandin synthesis inhibitors. The interaction of the kallikrein-kinin system with salt retaining steroids and the dependence of kinin effect on positive sodium balance will be assessed on the tubular level. Intrarenal kinin generation will be altered by administering kinin and kallikrein antibodies and by a peptidyl dipeptidase inhibitor. These studies will allow us to define more fully the possible participation of local hormonal factors in the regulation of renal excretory functions and their contribution to body fluid and electrolyte balance and, consequently, to blood pressure control.